过滤机错气、吹气系统泄漏原因？
参考答案：
1）错气盘腐蚀坏；2）吹气嘴磨蚀或弹簧坏。
简述急性肺水肿的抢救配合与护理
He has been hoping for a rise in salary for years but he ( ) ask for it yet.
A．doesn't dare
B．daren't
C．won't dare
D．hadn't dared
